The present invention relates to a steel laminate type cylinder head gasket for an internal combustion engine with an auxiliary combustion chamber.
An engine with an auxiliary combustion chamber is known, which comprises, as shown in FIG. 1, a cylinder block J having at least one cylinder bore Hc, a cylinder head H having a depression K, and a mouth plate L attached to the cylinder head H to cover the depression K for constituting an auxiliary combustion chamber M. A gasket 10 is installed between the cylinder head H and the cylinder block J. As a result, the gasket 10 supports a part N of the mouth plate L (FIG. 2). Namely, the part N of the mouth plate L is located on and supported by the gasket 10.
When the mouth plate L is installed in the cylinder head H, a lower surface of the cylinder head H must be precisely flush with a lower surface of the mouth plate L. Otherwise, sealing around the cylinder bore Hc of the cylinder block J can not be securely made.
Actually, it is very difficult to prepare the cylinder head H and the mouth plate L so that the lower surfaces thereof are flush with each other. Generally, the lower surface of the mouth plate L slightly projects or dents from the lower surface of the cylinder head H. Moreover, even if the lower surfaces of the cylinder head H and the mouth plate L are flush with each other when the mouth plate L is installed in the cylinder head H, in case the engine is operated, the lower surfaces of the cylinder head H and the mouth plate L do not become flush with each other due to heat of the engine.
Under the circumstances, unless a gasket situated between the cylinder head H and the cylinder block J can provide sufficient elasticity in any situation, sealing around the cylinder head H, cylinder block J and mouth plate L can not be properly made. However, since a conventional steel laminate gasket 10 as shown in FIG. 1 is formed of a plurality of steel plates and a wire ring, the steel laminate gasket 10 can not provide sufficient elasticity to properly seal around the cylinder bore. Therefore, it was desired to provide a steel laminate gasket which can securely seal around the cylinder bore.
In view of the drawbacks of the conventional steel laminate gasket, an improved steel laminate gasket is proposed in Japanese patent application No. 57-199777 (published on May 25, 1984 as Publication No. 59-90745), wherein one of plates forming a steel laminate gasket is provided with a plurality of projections or beads at an area P' corresponding to the part N of the mouth plate L. As shown in FIG. 3, beads 11 are concentrically arranged at the part P' of a plate 12.
The steel laminate gasket with the beads 11 as disclosed in Publication No. 59-90745 can properly seal around the cylinder bore Hc, as compared with a steel laminate gasket without beads. However, the steel laminate gasket with the beads 11 can not perfectly seal.
As a result of study, it was noticed that when the engine with the auxiliary combustion chamber is operated, the mouth plate L may move toward the auxiliary combustion chamber. In particular, the center of the mouth plate L dents deepest, and the dent becomes shallower as it goes toward the edge of the mouth plate L. This is because the mouth plate L separating the combustion chamber from the auxiliary combustion chamber is severely affected by heat and pressure changes of the combustion chamber. The steel laminate gasket with the beads 11 as disclosed in Publication No. 59-90745 could not properly absorb the movement of the mouth plate L caused by the heat and pressure changes of the combustion chamber. Namely, the gasket with the beads 11 can seal a shallow portion of a dent but can not seal a deep portion thereof. Consequently, gas leakage may happen.
Further, when high temperature and pressure are applied to the mouth plate, the mouth plate may deform. The conventional gasket can not seal around the mouth plate when the mouth plate L is deformed. Gas leakage happens especially at portions where the outer periphery of the mouth plate L intersects the outer periphery of the cylinder bore Hc.
Accordingly, one object of the present invention is to provide a steel laminate gasket for an engine with an auxiliary combustion chamber, which can seal properly around the entire cylinder bore.
Another object of the present invention is to provide a steel laminate gasket as stated above, wherein different sealing pressure applied to the gasket can be properly absorbed.
A further object of the present invention is to provide a steel laminate gasket as stated above, wherein even if the mouth plate is deformed, a seal around the mouth plate can be properly made.
A still further object of the present invention is to provide a steel laminate gasket as stated above, wherein the gasket can be easily and economically manufactured.
Further objects and advantages of the invention will be apparent from the following description of the invention.